Improved detection & display of data types

[dannyparsons]

fixes #6266

• Symbols now in upper case
• Dates group expanded to date and time related columns
• Added (S) for structured (circular only for now)
• Added (A) for application (not implemented yet)

@africanmathsinitiative/developers this is ready for review

[rdstern]

It seems to work fine, so I approve.
I tried with data and should say I don't like the use of capital letters any more than I think they are frowned on by tidyverse? It isn't so bad for D, but having lots of F and O.F and C is a bit shouty?

[dannyparsons]

It is a bit, but I think it adds clarity. It's probably more noticeable for existing users who are used to the lower case.
We already use it for D and also we had to have L for logical because "l" wasn't clear. So if we want consistency capitals is the only way to go. But I'm not completely against mixing upper and lower.

Could we try it out up to the next release and if you're still not convinced we go back to some lower case?

[lloyddewit]

@rdstern Please could you test/approve again? thanks